Design of a visible dual broadband nearly perfect absorber

Many optical systems benefit from elements that can absorb a broad range of wavelengths over a wide range of angles, independent of polarization. In this paper, we present a nearly perfect absorber with dual broadband and polarization-independent in the visible regime that exploits strong symmetric and asymmetric resonance modes of electromagnetic dipoles. It makes use of a bilayer hollowed-out cross pattern structure which is simple, having five layers that include two stacks of metal film with hollowed-out ribbon in cross patterns, two dielectric spacers, and a metal reflecting layer. Simulations show that the design exhibits a significantly enhanced absorption property when compared to a device with a normal cross pattern structure. The nearly perfect absorption efficiency of the device is above 98.5% at two resonances regimes: from 5.57 × 10¹⁴to 6.08 × 10¹⁴Hz and from 6.75 × 10¹⁴to 7.05 × 10¹⁴Hz, and its stable absorption characteristics can be maintained over a wide range of polarizing angle – up to ±90°. This strategy can, in principle, be applied to other material systems and could be useful in diverse applications, including thermal emitters, photovoltaics, and photodetectors.